Three axis magnetic field sensor

ABSTRACT

Three bridge circuits ( 101, 111, 121 ), each include magnetoresistive sensors coupled as a Wheatstone bridge ( 100 ) to sense a magnetic field ( 160 ) in three orthogonal directions ( 110, 120, 130 ) that are set with a single pinning material deposition and bulk wafer setting procedure. One of the three bridge circuits ( 121 ) includes a first magnetoresistive sensor ( 141 ) comprising a first sensing element ( 122 ) disposed on a pinned layer ( 126 ), the first sensing element ( 122 ) having first and second edges and first and second sides, and a first flux guide ( 132 ) disposed non-parallel to the first side of the substrate and having an end that is proximate to the first edge and on the first side of the first sensing element ( 122 ). An optional second flux guide ( 136 ) may be disposed non-parallel to the first side of the substrate and having an end that is proximate to the second edge and the second side of the first sensing element ( 122 ).

PRIORITY

This application is a continuation reissue application of U.S. Reissueapplication Ser. No. 15/165,600, filed on May 26, 2016, which is acontinuation reissue application of U.S. Reissue application Ser. No.14/638,583, filed on Mar. 4, 2015 (now U.S. Reissue Pat. No. RE46,180),which is a reissue application of U.S. Pat. No. 8,390,283 B2, whichissued on Mar. 5, 2013, from U.S. patent application Ser. No.12/567,496, filed on Sep. 25, 2009, the entire disclosure of which isexpressly incorporated herein by reference.

More than one reissue application has been filed for the reissue of U.S.Pat. No. 8,390,283 B2. The reissue applications are the present reissueapplication, U.S. Reissue application Ser. No. 15/165,600, and U.S.Reissue application Ser. No. 14/638,583 (now U.S. Reissue Pat. No.RE46,180).

FIELD

The present invention generally relates to the field ofmagnetoelectronic devices and more particularly to CMOS-compatiblemagnetoelectronic field sensors used to sense magnetic fields in threeorthogonal directions.

BACKGROUND

Sensors are widely used in modern systems to measure or detect physicalparameters, such as position, motion, force, acceleration, temperature,pressure, etc. While a variety of different sensor types exist formeasuring these and other parameters, they all suffer from variouslimitations. For example, inexpensive low field sensors, such as thoseused in an electronic compass and other similar magnetic sensingapplications generally consist of anisotropic magnetoresistance (AMR)based devices. In order to arrive at the required sensitivity andreasonable resistances that match well with CMOS, the sensing units ofsuch sensors are generally on the order of square millimeters in size.For mobile applications, such AMR sensor configurations are costly, interms of expense, circuit area, and power consumption.

Other types of sensors, such as Hall effect sensors, giantmagnetoresistance (GMR) sensors, and magnetic tunnel junction (MTJ)sensors, have been used to provide smaller profile sensors, but suchsensors have their own concerns, such as inadequate sensitivity andbeing effected by temperature changes. To address these concerns, MTJsensors and GMR sensors have been employed in a Wheatstone bridgestructure to increase sensitivity and to eliminate temperature dependentresistance changes. Many magnetic sensing technologies are inherentlyresponsive to one orientation of applied field, to the exclusion oforthogonal axes. Indeed, two-axis magnetic field sensors have beendeveloped for electronic compass applications to detect the earth'sfield direction by using a Wheatstone bridge structure for each senseaxis.

For example, Hall sensors are generally responsive to out-of-plane fieldcomponents normal to the substrate surface, while magneto-resistivesensors are responsive to in-plane applied magnetic fields. Utilizingthese responsive axes, development of a small footprint three axissensing solution typically involves a multi chip module with one or morechips positioned at orthogonal angles to one another. Formagnetoresistive sensors, the orthogonal in-plane components may beachieved with careful sensor design, but the out-of-plane response iscommonly garnered through vertical bonding or solder reflow to contact asecondary chip that has be mounted vertically. As the size of thevertically bonded chip is typically dominated by the pad pitch asdetermined from the handling constraints, such a technique results in alarge vertical extent of the finished package, high die and assemblycosts, and makes chip scale packaging difficult and costly as throughchip vias must be incorporated.

Accordingly, a need exists for an improved design and fabricationprocess for forming a single chip magnetic sensor that is responsive anapplied magnetic field in three dimensions. There is also a need for athree-axis sensor that can be efficiently and inexpensively constructedas an integrated circuit structure for use in mobile applications. Thereis also a need for an improved magnetic field sensor and fabrication toovercome the problems in the art, such as outlined above. Furthermore,other desirable features and characteristics of the present inventionwill become apparent from the subsequent detailed description and theappended claims, taken in conjunction with the accompanying drawings andthis background.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will hereinafter be described inconjunction with the following drawing figures, wherein like numeralsdenote like elements, and

FIG. 1 illustrates an electronic compass structure which usesdifferential sensors formed from three bridge structures with MTJsensors in accordance with an exemplary embodiment;

FIG. 2 is a partial cross section of the Z axis bridge structure of FIG.1 in accordance with the exemplary embodiment;

FIG. 3 is a view of flux lines as calculated by finite elementsimulation of two of the four magnetic tunnel junction sensors of FIG. 2;

FIG. 4 is a partial cross section of the Z axis bridge structure of FIG.1 in accordance with another exemplary embodiment;

FIG. 5 is a partial cross section of the Z axis bridge structure of FIG.1 in accordance with yet another exemplary embodiment;

FIG. 6 is another shape of a flux guide as shown in FIG. 5 ;

FIG. 7 is yet another shape of the flux guide as shown in FIG. 5 ;

FIG. 8 is still another shape of the flux guide as shown in FIG. 5 ; and

FIG. 9 is a graph illustrating the Z sensitivity expressed as apercentage of the X sensitivity for a single (not differentially wired)MTJ sense element as a function of the cladding to sensor spacing.

It will be appreciated that for simplicity and clarity of illustration,elements illustrated in the drawings have not necessarily been drawn toscale. For example, the dimensions of some of the elements areexaggerated relative to other elements for purposes of promoting andimproving clarity and understanding. Further, where consideredappropriate, reference numerals have been repeated among the drawings torepresent corresponding or analogous elements.

SUMMARY

A ferromagnetic thin-film based magnetic field sensor includes a firstmagnetoresistive sensor comprising a substrate having a planar surface,and a first sensing element having a first side lying parallel to theplanar surface of the substrate, the first sensing element having asecond side opposed to the first side and having first and secondopposed edges; and a first flux guide disposed non-parallel to the firstside of the substrate and having an end that is proximate to the firstedge and the first side of the first sensing element. An optional secondflux guide may be disposed non-parallel to the first side of thesubstrate and having an end that is proximate to the second edge and thesecond side of the first sensing element.

In another exemplary embodiment, a ferromagnetic thin-film basedmagnetic field sensor includes first, second, and third magnetoresistivesensors. The first magnetic tunnel junction sensor includes a firstpinned layer and a first sensing element formed on the first pinnedlayer, the second magnetic tunnel junction sensor includes a secondpinned layer and a second sensing element formed on the second pinnedlayer and orthogonal to the first sensing element, and the thirdmagnetic tunnel junction sensor includes a third pinned layer and athird sensing element formed on the third pinned layer, the third pinnedlayer disposed at about 45 degrees to each of the first and secondpinned layers, the third sensing element having first and second edgesand first and second sides. A flux guide is disposed non-parallel to aplanar surface of the substrate and has an end that is proximate to thefirst edge and the first side of the third sensing element.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by any theorypresented in the preceding background or the following detaileddescription.

Through the integration of high aspect ratio vertical bars (flux guides)of a high permeability material, for example, nickel iron (NiFe), whoseends terminate in close proximity to opposed edges and opposite sides ofa magnetic sense element, a portion of the Z axis field can be broughtinto the XY plane. These flux guides serve to capture magnetic flux froman applied field oriented in the Z direction, and in so doing, bend thefield lines in a substantially horizontal manner near the ends of theflux guides. Through asymmetric positioning of the flux guides, e.g.,the flux guide segment above the left edge of sense elements in two legsof the four legs of a Wheatstone bridge, and the flux guide above theright edge of sense elements in the other two legs, the horizontalcomponents may act in an opposite directions for the two pairs of legsresulting in a strong differential signal. A field applied in the X or Ydirection will project equally on all four legs of the bridge and hencebe subtracted out and not contribute to the final sensor signal.Separate bridges are included elsewhere on the magnetic sensor chip fordetermining the X and Y components of the magnetic signal, and in thismanner, a field with components in all three spatial orientations can beaccurately determined by a single chip magnetoresistive sensing module,for example, based on magnetic tunnel junction (MTJ) sense elements.Finite Element Method (FEM) simulations have shown that a pair of highaspect ratio flux guides, e.g., 25 nm wide by 500 nm high and extendingseveral microns in the third direction, when optimally positioned willprovide a signal on an individual element that is about 80% of the ofthe signal measured from an in plane (x axis) field of the samestrength. Additional signal may be obtained through closer proximity ofthe flux guide to the sensor, increases in the flux guide height, andadditional shaping of the guide geometry. One example is to addhorizontal segments parallel to the sense element which extend over theedges of the sense element. Other examples are to form a U which isplaced with the interior horizontal segment aligned with the outer edgeof the sense element, angled termination of the vertical segments toextend the flux guide partially in the plane of the sense element, and asimilarly placed box structure. These geometries serve to furtherenhance the horizontal component of the guided flux and move it to amore central region of the sensor. A structure with individual 25 nmwide vertical bars utilized as flux guides is tolerant to overlay errorsand produces an apparent x to z field conversion (for a differentiallywired Wheatstone bridge) at the rate of 2.5% for a misalignment of 85 nm(3 sigma) between a single flux guiding layer and the sense layer.

The flux guiding layer may be formed from layers typically used in themagnetic random access memory (MRAM) process flow, during which bit anddigit lines cladded with a high permeability magnetic material (such asin typical magnetic memory devices), referred to herein as a flux guide,are used to increase the field factors present to reduce the currentneeded to switch the memory storage element. In the sensor application,the same process flow may be used with the optional additional step ofsputtering out the bottom of the digit line in order to remove anycladding present on the trench's bottom. Modifications may be made tothe process flow so that the height and width of the cladding used forflux guiding are at optimum values instead of the 500 nm and 25 nm,respectively that are used in the exemplary process described above.

A method and apparatus are subsequently described in more detail forproviding multi-axis pinning on a bulk wafer which may be used to forman integrated circuit sensor with different reference layers havingthree different pinning directions, two of which are substantiallyorthogonal that are set with a single pinning material deposition andbulk wafer setting procedure. As a preliminary step, a stack of one ormore layers of ferromagnetic and antiferromagnetic materials are etchedinto shaped reference layers having a two-dimensional shape with a highaspect ratio, where the shape provides a distinction for the desiredmagnetization direction for each reference layer. Depending on thematerials and techniques used, the final magnetization direction may beoriented along the short axis or the long axis of the shaped layer. Forexample, if the pinned layer is formed with a slightly imbalancedsynthetic anti-ferromagnet (SAF) patterned into micron-scale dimensions,the magnetization will direct along the short axis. As will beappreciated by those skilled in the art, the SAF embodiment provides anumber of benefits related to the use of pinned-SAF reference layers inmagnetoelectronic devices. In other embodiments, by controlling thethicknesses of the pinned and fixed layers and the in-plane spatialextent of the patterned structure, the final magnetization may bedirected along the long axis. Using shape anisotropy, differentmagnetization directions are induced in the reference layers by heatingin the presence of an orienting field that is aligned between thedesired magnetization directions for the reference layers. In selectedembodiments, the reference layers are heated sufficiently to reduce thematerial component of the anisotropy and allow the shape and externalfield to dominate the magnetization direction. In this manner, once theorienting field is removed, the shape anisotropy directs themagnetization in the desired direction. Upon removing the orientingfield, the magnetizations of the reference layers relax to follow theshape of the reference layers so as to induce a magnetization that isaligned along the desired axis of the shaped reference layer. Anoptional compensating field may be applied to help induce orthogonality,and the reference layers are then heated to above the phase transitiontemperature of the antiferromagnetic pinning layers. For example, if tworeference layers are shaped to have longer dimensions which areperpendicular to one another, then the induced magnetizations for thetwo reference layers will be close to being perpendicular to oneanother.

Various illustrative embodiments of the present invention will now bedescribed in detail with reference to the accompanying figures. Whilevarious details are set forth in the following description, it will beappreciated that the present invention may be practiced without thesespecific details, and that numerous implementation-specific decisionsmay be made to the invention described herein to achieve the devicedesigner's specific goals, such as compliance with process technology ordesign-related constraints, which will vary from one implementation toanother. While such a development effort might be complex andtime-consuming, it would nevertheless be a routine undertaking for thoseof ordinary skill in the art having the benefit of this disclosure. Inaddition, selected aspects are depicted with reference to simplifiedcross sectional drawings without including every device feature orgeometry in order to avoid limiting or obscuring the present invention.It is also noted that, throughout this detailed description,conventional techniques and features related to magnetic sensor designand operation. Magnetoresistive Random Access Memory (MRAM) design, MRAMoperation, semiconductor device fabrication, and other aspects of theintegrated circuit devices may not be described in detail herein. Whilecertain materials will be formed and removed to fabricate the integratedcircuit sensors as part of an existing MRAM fabrication process, thespecific procedures for forming or removing such materials are notdetailed below since such details are well known and not considerednecessary to teach one skilled in the art of how to make or use thepresent invention. Furthermore, the circuit/component layouts andconfigurations shown in the various figures contained herein areintended to represent exemplary embodiments of the invention. It shouldbe noted that many alternative or additional circuit/component layoutsmay be present in a practical embodiment.

FIG. 1 shows a magnetic field sensor 100 formed with first, second, andthird differential sensors 101, 111, 121 for detecting the componentdirections of an applied field along a first axis 120 (e.g., the y-axisdirection), a second axis 110 (e.g., the x-axis direction), and a thirdaxis 130 (e.g., the z-axis direction), respectively. The z-axisdirection is represented as a dot and cross-hairs as going either intoor out of the page on which FIG. 1 is situated. Exemplary embodiments ofthe first and second sensors 101, 111 are described in detail in U.S.patent application Ser. No. 12/433,679. As depicted herein, each sensor101, 111, 121 is formed with unshielded sense elements that areconnected in a bridge configuration. Thus, the first sensor 101 isformed from the connection of a plurality of sense elements 102-105 in abridge configuration over a corresponding plurality of pinned layers106-109, where each of the pinned layers 106-109 is magnetized in thex-axis direction. In similar fashion, the second sensor 111 is formedfrom the connection of a plurality of sense elements 112-115 in a bridgeconfiguration over a corresponding plurality of pinned layers 116-119that are each magnetized in the y-axis direction that is perpendicularto the magnetization direction of the pinned layers 106-109.Furthermore, the third sensor 121 in the same plane as the first andsecond sensors 101, 111 is formed from the connection of a plurality ofsense elements 122-125 in a bridge configuration over a correspondingplurality of pinned layers 126-129 that are each magnetized in thexy-axis direction that is at 45 degrees to the magnetization directionof the pinned layers 106-109 and 116-119. In the depicted bridgeconfiguration 101, the sense elements 102, 104 are formed to have afirst easy axis magnetization direction and the sense elements 103, 105are formed to have a second easy axis magnetization direction, where thefirst and second easy axis magnetization directions are orthogonal withrespect to one another and are oriented to differ equally from themagnetization direction of the pinned layers 106-109. As for the secondbridge configuration 111, the sense elements 112, 114 have a first easyaxis magnetization direction that is orthogonal to the second easy axismagnetization direction for the sense elements 113, 115 so that thefirst and second easy axis magnetization directions are oriented todiffer equally from the magnetization direction of the pinned layers116-119. In the third bridge configuration 121, the sense elements 122123,124, and 125 all have an easy axis magnetization direction that isorthogonal to the pinned magnetization direction of the pinned layers126, 127, 128, and 129. The third bridge configuration 121 furtherincludes flux guides 132-135 positioned adjacent to the right edge ofsense elements 122-125, and flux guides 136-139 positioned adjacent tothe left edge of sense elements 122-125, respectively. Flux guides132,137, 134, and 139 are positioned above sense elements 122-125, andflux guides 136, 133, 138, and 135 are positioned below sense elements122-125. The positioning of these flux guides 132-139 is subsequentlydescribed in more detail in FIG. 2 . In the depicted sensors 101, 111,121 there is no shielding required for the sense elements, nor are anyspecial reference elements required. In an exemplary embodiment, this isachieved by referencing each active sense element (e.g., 102, 104) withanother active sense element (e.g., 103, 105) using shape anisotropytechniques to establish the easy magnetic axes of the referenced senseelements to be deflected from each other by 90 degrees for the x and ysensors, and referencing a sense element that responds in an oppositemanner to an applied field in the Z direction for the Z sensor. The Zsensor referencing will be described in more detail below. Theconfiguration shown in FIG. 1 is not required to harvest the benefits ofthe third sensor 121 structure described in more detail in FIG. 2 , andis only given as an example.

By positioning the first and second sensors 101, 111 to be orthogonallyaligned, each with the sense element orientations deflected equally fromthe sensor's pinning direction and orthogonal to one another in eachsensor, the sensors can detect the component directions of an appliedfield along the first and second axes. Flux guides 132-139 arepositioned in sensor 121 above and below the opposite edges of theelements 122-125, in an asymmetrical manner between legs 141, 143 andlegs 142, 144. As flux guides 132, 134 are placed above the senseelements 122, 124, the magnetic flux from the Z field may be guided bythe flux guides 132 and 134 into the xy plane along the right side andcause the magnetization of sense elements 122 and 124 to rotate in afirst direction towards a higher resistance. Similarly, the magneticflux from the Z field may be guided by the flux guides 133 and 135 intothe xy plane along the right side of the sense element and cause themagnetization of sense elements 123 and 125 to rotate in a seconddirection, opposite from the first direction towards a lower resistance,as these flux guides are located below the sense elements 123, 125.Thus, the sensor 121 can detect the component directions of an appliedfield along the third axis. Although in the preferred embodiment, theflux guides are in a plane orthogonal to the plane of the field sensor,the flux guides will still function if the angle they make with thesensor is not exactly 90 degrees. In other embodiments, the anglebetween the flux guide and the field sensor could be in a range from 45degrees to 135 degrees, with the exact angle chosen depending on otherfactors such as on the ease of fabrication.

As seen from the foregoing, a magnetic field sensor may be formed fromdifferential sensors 101, 111, 121 which use unshielded sense elements102-105, 112-115, and sense elements 122-125 with guided magnetic fluxconnected in a bridge configuration over respective pinned, orreference, layers 106-109, 116-119, and 126-129 to detect the presenceand direction of an applied magnetic field. With this configuration, themagnetic field sensor provides good sensitivity, and also provides thetemperature compensating properties of a bridge configuration.

The bridge circuits 101, 111, 121 may be manufactured as part of anexisting MRAM or thin-film sensor manufacturing process with only minoradjustments to control the magnetic orientation of the various sensorlayers and cross section of the flux guiding structures. Each of thepinned layers 106-109, 116-119, and 126-129 may be formed with one ormore lower ferromagnetic layers, and each of the sense elements 102-105,112-125, 122-125 may be formed with one or more upper ferromagneticlayers. An insulating tunneling dielectric layer (not shown) (e.g., 200,201, 202, and 203 shown in FIG. 2) may be disposed between the senseelements 102-105, 112-125, 122-125 and the pinned layers 106-109,116-119, and 126-129. The pinned and sense electrodes are desirablymagnetic materials whose magnetization direction can be aligned.Suitable electrode materials and arrangements of the materials intostructures commonly used for electrodes of magnetoresistive randomaccess memory (MRAM) devices and other magnetic tunnel junction (MTJ)sensor devices are well known in the art. For example, pinned layers106-109, 116-119, and 126-129 may be formed with one or more layers offerromagnetic and antiferromagnetic materials to a combined thickness inthe range 10 to 1000 Å, and in selected embodiments in the range 250 to350 Å. In an exemplary implementation, each of the pinned layers106-109, 116-119, and 126-129 is formed with a single ferromagneticlayer and an underlying anti-ferromagnetic pinning layer. In anotherexemplary implementation, each pinned layer 106-109, 116-119, and126-129 includes a synthetic anti-ferromagnetic stack component (e.g., astack of CF (Cobalt Iron), Ruthenium (Ru) and CFB) which is 20 to 80 Åthick, and an underlying anti-ferromagnetic pinning layer that isapproximately 200 Å thick. The lower anti-ferromagnetic pinningmaterials may be re-settable materials, such as IrMn, though othermaterials, such as PtMn, can be used which are not readily re-set atreasonable temperatures. As formed, the pinned layers 106-109, 116-119,and 126-129 function as a fixed or pinned magnetic layer when thedirection of its magnetization is pinned in one direction that does notchange during normal operating conditions. As disclosed herein, theheating qualities of the materials used to pin the pinned layers106-109, 116-119, and 126-129 can change the fabrication sequence usedto form these layers.

One of each of the sense elements 102-105, 112-125, 122-125 and one ofeach of the pinned layers 106-109, 116-119, 126-129 form a magnetictunnel junction (MTJ) sensor. For example, for bridge circuit 121, senseelement 122 and pinned layer 126 form an MTJ sensor 141. Likewise, senseelement 123 and pinned layer 127 form an MTJ sensor 142, sense element124 and pinned layer 128 form an MTJ sensor 143, and sense element 125and pinned layer 129 form an MTJ sensor 144.

The pinned layers 106-109, 116-119, and 126-129 may be formed with asingle patterned ferromagnetic layer having a magnetization direction(indicated by the arrow) that aligns along the long-axis of thepatterned reference layer(s). However, in other embodiments, the pinnedreference layer may be implemented with a synthetic anti-ferromagnetic(SAF) layer which is used to align the magnetization of the pinnedreference layer along the short axis of the patterned referencelayer(s). As will be appreciated, the SAF layer may be implemented incombination with an underlying anti-ferromagnetic pinning layer, thoughwith SAF structures with appropriate geometry and materials that providesufficiently strong magnetization, the underlying anti-ferromagneticpinning layer may not be required, thereby providing a simplerfabrication process with cost savings.

The sense elements 102-105, 112-125, 122-125 may be formed with one ormore layers of ferromagnetic materials to a thickness in the range 10 to5000 Å, and in selected embodiments in the range 10 to 60 Å. The upperferromagnetic materials may be magnetically soft materials, such asNiFe, CoFe, Fe, CFB and the like. In each MTJ sensor, the sense elements102-105, 112-125, 122-125 function as a sense layer or free magneticlayer because the direction of their magnetization can be deflected bythe presence of an external applied field, such as the Earth's magneticfield. As finally formed, sense elements 102-105, 112-125, 122-125 maybe formed with a single ferromagnetic layer having a magnetizationdirection (indicated with the arrows) that aligns along the long-axis ofthe patterned shapes.

The pinned layers 106-109, 116-119, 126-129 and sense elements 102-105,112-125, 122-125 may be formed to have different magnetic properties.For example, the pinned layers 106-109, 116-119, 126-129 may be formedwith an antiferromagnetic film exchange layer coupled to a ferromagneticfilm to form layers with a high coercive force and offset hysteresiscurves so that their magnetization direction will be pinned in onedirection, and hence substantially unaffected by an externally appliedmagnetic field. In contrast, the sense elements 102-105, 112-125,122-125 may be formed with a magnetically soft material to providedifferent magnetization directions having a comparatively low anisotropyand coercive force so that the magnetization direction of the senseelectrode may be altered by an externally applied magnetic field. Inselected embodiments, the strength of the pinning field is about twoorders of magnitude larger than the anisotropy field of the senseelectrodes, although different ratios may be used by adjusting therespective magnetic properties of the electrodes using well knowntechniques to vary their composition.

The pinned layers 106-109, 116-119, 126-129 in the MTJ sensors areformed to have a shape determined magnetization direction in the planeof the pinned layers 106-109, 116-119, 126-129 (identified by the vectorarrows for each sensor bridge labeled “Pinning direction” in FIG. 1 ).As described herein, the magnetization direction for the pinned layers106-109, 116-119, 126-129 may be obtained using shape anisotropy of thepinned electrodes, in which case the shapes of the pinned layers106-109, 116-119, 126-129 may each be longer in the pinning directionfor a single pinned layer. Alternatively, for a pinned SAF structure,the reference and pinned layers may be shorter along the pinningdirection. In particular, the magnetization direction for the pinnedlayers 106-109, 116-119, 126-129 may be obtained by first heating theshaped pinned layers 106-109, 116-119, 126-129 in the presence of aorienting magnetic field which is oriented non-orthogonally to the axisof longest orientation for the shaped pinned layers 106-109, 116-119,126-129 such that the applied orienting field includes a field componentin the direction of the desired pinning direction for the pinned layers106-109, 116-119, 126-129. The magnetization directions of the pinnedlayers are aligned, at least temporarily, in a predetermined direction.However, by appropriately heating the pinned layers during thistreatment and removing the orienting field without reducing the heat,the magnetization of the pinned layers relaxes along the desired axis oforientation for the shaped pinned pinned layers 106-109, 116-119,126-129. Once the magnetization relaxes, the pinned layers can beannealed and/or cooled so that the magnetic field direction of thepinned electrode layers is set in the desired direction for the shapedpinned layers 106-109, 116-119, 126-129.

The exemplary embodiments described herein may be fabricated using knownlithographic processes as follows. The fabrication of integratedcircuits, microelectronic devices, micro electro mechanical devices,microfluidic devices, and photonic devices involves the creation ofseveral layers of materials that interact in some fashion. One or moreof these layers may be patterned so various regions of the layer havedifferent electrical or other characteristics, which may beinterconnected within the layer or to other layers to create electricalcomponents and circuits. These regions may be created by selectivelyintroducing or removing various materials. The patterns that define suchregions are often created by lithographic processes. For example, alayer of photoresist material is applied onto a layer overlying a wafersubstrate. A photomask (containing clear and opaque areas) is used toselectively expose this photoresist material by a form of radiation,such as ultraviolet light, electrons, or x-rays. Either the photoresistmaterial exposed to the radiation, or that not exposed to the radiation,is removed by the application of a developer. An etch may then beapplied to the layer not protected by the remaining resist, and when theresist is removed, the layer overlying the substrate is patterned.Alternatively, an additive process could also be used, e.g., building astructure using the photoresist as a template.

Referring to FIG. 2 and in accordance with an exemplary embodiment ofthe present invention, the structure of the MTJ devices 141-144 of thethird bridge circuit 121 include the pinned layers 126-129, the senseelements 122-125, and the flux guides 132-139, all formed within thedielectric material 140. The flux guide 136 is positioned adjacent aline 145 and has an end positioned below an edge of the sensor element122. The flux guides 133 and 138 are positioned on opposed sides of aline 146 and have ends positioned below edges of the sensor elements 123and 124, respectively. The flux guide 135 is positioned adjacent a line147 and has an end positioned below an edge of the sensor element 125.The flux guides 132 and 137 are spaced apart by an upper line 148 andhave ends positioned above edges of the sensor elements 122 and 123,respectively, and the flux guides 134 and 139 are spaced apart by anupper line 149 and have ends positioned above edges of the sensorelements 134 and 139, respectively. The lines 145-149, are preferablycopper, but in some embodiments may be a dielectric. A metalstabilization line 150 is positioned above the MTJ devices 141-144 forproviding a stabilization field to the sense elements. The ends of theflux guides may be brought as close as possible to the sensor elements,with a preferable spacing of less than or equal to 250 nm between thetwo. The sense elements are brought as close as possible for thetightest density array, preferably less than 2.5 um apart.

FIG. 3 is a view of flux lines as calculated by finite elementsimulation of MTJ devices 141, 142 of FIG. 2 with a magnetic field inthe z direction imparted upon the sense elements 122-123. FEM modelingshows the resultant magnetic flux lines 160, exhibiting a component inthe plane of the sensor. MTJ device 141 is represented by flux guides132 and 136 on opposed ends of the sensing element 122. MTJ device 142is represented by flux guides 133 and 137 on opposed ends of the sensingelement 123. Stated otherwise, sensing element 122 extends from fluxguides 132 and 136, and sensing element 123 extends from flux guides 133and 137. The magnetic field 160 in the Z-axis 130 produces an asymmetricresponse in the sensing elements 122, 123 along the X-axis 120 asindicated by the arrows 170. In this manner, for a field 160 in the Zdirection 130 directed towards the bottom of the page, the magnetizationof sense element 122 rotates away from the pinning direction (and tohigher resistance) of the pinned layer 126, while the magnetization ofsense element 123 rotates towards the pinning direction (and to lowerresistance) of pinned layer 127. For a field in the X direction 120,both elements 122, 123 show induced magnetization in the same direction(towards higher or lower resistance). Therefore, by wiring MTJ elements141, 142 in a Wheatstone bridge for differential measurement andsubtracting the resistances of MTJ devices 141, 142, the X fieldresponse is eliminated and twice the Z field response is measured.

Referring again to FIG. 2 , in the case of an exposure to a largemagnetic field which may induce magnetization disturbances and domainstructure in the flux guides 132-139, a large current pulse may beintroduced along metal lines 145-149 to reset the flux guide domainstructure.

In another exemplary embodiment (shown in FIG. 4 ), each of the claddedlines 145-149 are divided into two independent metal lines, andadditional non-flux guiding cladding (161-168 and 191-198) is placed inbetween these two metal lines at the interior edges. For sensor 141, theflux guide 161 on the left edge of the left metal line, 148 guides Zfield flux into the sense element 122 to its left, and the flux guide192 on the right most edge of the right metal line 145 guides Z fieldflux into the sense element 122 on its right. Sensors 142-144 functionsimilarly, with the cladded edge of the metal line adjacent to eachsense element serving the active flux guiding function. As these linesare separated, a current may be made to pass through cladded lines 145,146, 182 and 183 into the page, and 181, 147, 148, and 149 out of thepage to create a magnetic field along the cladded line edges with a Zcomponent pointing in a consistent direction (down in this example).These current orientations can serve to create a magnetic field with astrong component in the Z direction, which, through a calibration forthe geometry can serve as a self test for the functionality andsensitivity of the Z axis response.

Another exemplary embodiment (see FIG. 5 ) includes extensions 152-159integrally formed with the flux guides 132-139. The extensions 152-159extend along the same axis as the sensor elements 122-125 and accentuatethe horizontal component of the flux guide and move the horizontalcomponent more to the center of the appropriate sense element 122-125.

While various exemplary embodiments have been shown for the flux guides,including the vertical elements 132-139 of FIG. 2 , and the “L” shapedflux guides including extensions 152-159 of FIG. 5 , other exemplaryembodiments may be used for both upper and lower flux guides, such asbox shaped or “U” shaped flux guides. In the “U” shaped structure (FIG.6 ), a horizontal NiFe segment 171 connects the two vertical segments161, 162 along the bottom metal line, while in the box shaped structure(FIG. 7 8), a horizontal segment 172 connects the two vertical segmentsboth above the metal line as well. A horizontal segment helps to couplethe magnetic structure of the two vertical segments, increasing thefield conversion factor by 10-20% over that of two isolated verticalflux guides. Two horizontal segments of the box like structure providebetter coupling and increase the field conversion factor by twenty toforty percent over a simple vertical flux guide. Additionally, thevertical segments of the “U” shaped structure of FIG. 6 may be flared173, 174 (FIG. 8 7) out so that the region near the sense element edgehas a horizontal component. Similar to the L shaped guides, the flaredsegments guide the magnetic flux so that there is a component directlyin the plane of the magnetic sensor to further amplify the fieldconversion factor. However, care must be taken that the overlay is nottoo great or the magnetic flux will be shielded from the sensor.

FIG. 9 is a graph showing the Z/X sensitivity ratio versus thecladding/sensor spacing for a 25 nm wide, 500 nm tall vertical segmentsplaced above and below the sense element. The Z/X sensitivity increases,to about 75 percent, as the cladding is brought to 25 nanometers ofdistance. Additional factors may be gained through cross sectionalchanges such as those highlighted above, or through aspect ratioimprovements in the flux guide, for example, making the guide taller andincreasing the aspect ratio will linearly increase the Z/X sensitivityratio. Therefore, it is important to bring the flux guide as close aspossible to the sense element, and increase its aspect ratio as much asis possible without adversely impacting the magnetic microstructure.

Although the described exemplary embodiments disclosed herein aredirected to various sensor structures and methods for making same, thepresent invention is not necessarily limited to the exemplaryembodiments which illustrate inventive aspects of the present inventionthat are applicable to a wide variety of semiconductor processes and/ordevices. Thus, the particular embodiments disclosed above areillustrative only and should not be taken as limitations upon thepresent invention, as the invention may be modified and practiced indifferent but equivalent manners apparent to those skilled in the arthaving the benefit of the teachings herein. For example, the relativepositions of the sense and pinning layers in a sensor structure may bereversed so that the pinning layer is on top and the sense layer isbelow. Also the sense layers and the pinning layers may be formed withdifferent materials than those disclosed. Moreover, the thickness of thedescribed layers may deviate from the disclosed thickness values.Accordingly, the foregoing description is not intended to limit theinvention to the particular form set forth, but on the contrary, isintended to cover such alternatives, modifications and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims so that those skilled in the art shouldunderstand that they can make various changes, substitutions andalterations without departing from the spirit and scope of the inventionin its broadest form.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims. As used herein, the terms“comprises,” “comprising,” or any other variation thereof, are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or exemplary embodiments are only examples, and arenot intended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing an exemplary embodiment of the invention, it beingunderstood that various changes may be made in the function andarrangement of elements described in an exemplary embodiment withoutdeparting from the scope of the invention as set forth in the appendedclaims.

The invention claimed is:
 1. A ferromagnetic thin-film based magneticfield sensor comprising: a substrate having a planar surface; and afirst magnetoresistive sensor comprising: a first sensing element havinga first side lying parallel to the planar surface of the substrate, thefirst sensing element having a second side opposed to the first side andhaving first and second opposed edges; and a first flux guide comprisinga soft ferromagnetic material disposed non-parallel to the first side ofthe first sensing element and having an end that is proximate to thefirst edge and the first side of the first sensing element.
 2. Theferromagnetic thin-film based magnetic field sensor of claim 1 whereinthe first magnetoresistive sensor further comprises: a second flux guidecomprising a soft ferromagnetic material disposed non-parallel to thefirst side of the first sensing element and having an end that isproximate to the second edge and the second side of the first sensingelement.
 3. The ferromagnetic thin-film based magnetic field sensor ofclaim 1 wherein the first magnetoresistive sensor comprises one of anarray of ferromagnetic thin-film based magnetic field sensors.
 4. Theferromagnetic thin-film based magnetic field sensor of claim 1 whereinthe first flux guide comprises a high aspect ratio structurenon-parallel to the first sense element.
 5. The ferromagnetic thin-filmbased magnetic field sensor of claim 1 wherein the first flux guidecomprises a U shaped element.
 6. The ferromagnetic thin-film basedmagnetic field sensor of claim 1 wherein the first flux guide includes aflared end.
 7. The ferromagnetic thin-film based magnetic field sensorof claim 1 further comprising a material disposed adjacent the firstflux guide and comprising one of the group consisting of a highconductivity metal and a dielectric material.
 8. The ferromagneticthin-film based magnetic field sensor of claim 1 wherein the first fluxguide comprises a box shaped structure.
 9. The ferromagnetic thin-filmbased magnetic field sensor of claim 1 wherein at least one of the firstand second flux guides is disposed substantially orthogonal to the planeof the substrate.
 10. The ferromagnetic thin-film based magnetic fieldsensor of claim 1 wherein at least one of the first and second fluxguides is disposed at an angle of between 45 degrees and 90 degrees tothe plane of the substrate.
 11. The ferromagnetic thin-film basedmagnetic field sensor of claim 1 further comprising: a secondmagnetoresistive sensor having a second sensing element for detecting amagnetic field in a second direction orthogonal to the first direction;and a third magnetoresistive sensor having a third sensing elementorthogonal to the second sensing element for detecting a magnetic fieldin a third direction orthogonal to the first and second directions,wherein the third sensing element is in a plane with the first andsecond sensing elements.
 12. The ferromagnetic thin-film based magneticfield sensor of claim 11, wherein the first, second, and third sensorelements each comprise an imbalanced synthetic antiferromagnet formedwith first and second ferromagnetic layers separated by a spacer layer,where the first and second ferromagnetic layers have different magneticmoments.
 13. The ferromagnetic thin-film based magnetic field sensor ofclaim 1 further comprising: the first magnetoresistive sensorcomprising: a first pinned layer; a second magnetoresistive sensorcomprising: a second pinned layer; and a second sensing element formedon the second pinned layer; a third magnetoresistive sensor comprising:a third pinned layer; and a third sensing element formed on the thirdpinned layer and orthogonal to the second sensing element; wherein thesecond and third pinned layers are oriented about 45 degrees to thefirst pinned layer.
 14. The ferromagnetic thin-film based magnetic fieldsensor of claim 13 wherein the first magnetic tunnel junction furthercomprises: a second flux guide disposed non-parallel to the first sideof the first sensing element and having an end that is proximate to thesecond edge and the second side of the first sensing element.
 15. Theferromagnetic thin-film based magnetic field sensor of claim 14 whereinthe first and second flux guides each comprise an aspect ratio greaterthan
 10. 16. A ferromagnetic thin-film magnetic field sensor comprising:a first bridge circuit comprising first, second, third, and fourthmagnetic tunnel junction sensors coupled as a Wheatstone bridge forsensing a magnetic field orthogonal to the plane of the sensors; thefirst magnetic tunnel junction sensor comprising: a first referencelayer; and a first sensing element formed on the first reference layer,the first sensing element having first and second edges and first andsecond sides; and a first flux guide comprising a soft ferromagneticmaterial disposed orthogonal to and spaced from the first edge and thefirst side of the first sensing element; the second magnetic tunneljunction sensor comprising: a second reference layer; and a secondsensing element formed on the second reference layer, the second sensingelement having first and second edges and first and second sides; and asecond flux guide comprising a soft ferromagnetic material disposedorthogonal to and spaced from the first edge and the first side of thesecond sensing element; the third magnetic tunnel junction sensorcomprising: a third reference layer; and a third sensing element formedon the third reference layer, the third sensing element having first andsecond edges and first and second sides; and a third flux guidecomprising a soft ferromagnetic material disposed orthogonal to andspaced from the first edge and the first side of the third sensingelement; the fourth magnetic tunnel junction sensor comprising: a fourthreference layer; and a fourth sensing element formed on the fourthreference layer, the fourth sensing element having first and secondedges and first and second sides; and a fourth flux guide disposedorthogonal to and spaced from the first edge and the first side of thefourth sensing element.
 17. The ferromagnetic thin-film based magneticfield sensor of claim 16 wherein the first, second, third, and fourthmagnetic tunnel junction sensors further comprise fifth, sixth, seventh,and eighth flux guides disposed orthogonal to and spaced from the secondedge and the second side of the first, second, third, and fourth sensingelements, respectively.
 18. The ferromagnetic thin-film based magneticfield sensor of claim 16 further comprising: a second bridge circuitcomprising fifth, sixth, seventh, and eighth magnetic tunnel junctionsensors coupled as a second Wheatstone bridge for sensing a magneticfield in a second direction orthogonal to the first direction; and athird bridge circuit comprising, ninth, tenth, eleventh, and twelfthmagnetic tunnel junction sensors coupled as a third Wheatstone bridgefor sensing a magnetic field in a third direction orthogonal to thefirst and second directions.
 19. The ferromagnetic thin-film basedmagnetic field sensor of claim 16 wherein each of the first, second,third, and fourth sensors comprises an array of sense elements.
 20. Amethod of testing the functionality and sensitivity of a response of theZ axis of a ferromagnetic thin-film magnetic field sensor including asubstrate having a planar surface, and a first magnetoresistive sensorcomprising a sensing element having a first side lying parallel to theplanar surface of the substrate, the sensing element having a secondside opposed to the first side and having first and second opposededges, a first flux guide comprising a soft ferromagnetic materialdisposed non-parallel to the first side of the substrate and having anend that is proximate to the first edge and the first side of thesensing element, and a metal line formed adjacent contiguous to the fluxguide, the method comprising: applying a current through the metal lineto provide a magnetic field with a component parallel to the plane ofthe flux guides.
 21. The method of claim 20, further comprising:applying a current pulse through the metal line to reset the flux guidedomain structure.
 22. A ferromagnetic thin-film based magnetic fieldsensor comprising: a first plurality of magnetoresistive sensors coupledto sense a magnetic field in a first direction orthogonal to a plane ofthe first plurality of magnetoresistive sensors, wherein the firstplurality of magnetoresistive sensors includes first, second, third, andfourth magnetoresistive sensors; the first magnetoresistive sensorcomprising: a first sensing element, and a first flux guide comprising afirst soft ferromagnetic material, wherein the first soft ferromagneticmaterial is a first high permeability magnetic material, wherein (i) thefirst flux guide is above or below the first sensing element of thefirst magnetoresistive sensor in the first direction, (ii) the firstflux guide is disposed non-parallel to a first side of the first sensingelement, and (iii) the first flux guide includes an end that isproximate to a first edge and on the first side of the first sensingelement; the second magnetoresistive sensor comprising: a second sensingelement, and a second flux guide comprising a second soft ferromagneticmaterial, wherein the second soft ferromagnetic material is a secondhigh permeability magnetic material, wherein (i) the second flux guideis above or below the second sensing element of the secondmagnetoresistive sensor in the first direction, (ii) the second fluxguide is disposed non-parallel to a first side of the second sensingelement, and (iii) the second flux guide includes an end that isproximate to and on the first side of the second sensing element; thethird magnetoresistive sensor comprising: a third sensing element, and athird flux guide comprising a third soft ferromagnetic material, whereinthe third soft ferromagnetic material is a third high permeabilitymagnetic material, wherein (i) the third flux guide is above or belowthe third sensing element of the third magnetoresistive sensor in thefirst direction, (ii) the third flux guide is disposed non-parallel to afirst side of the third sensing element, and (iii) the third flux guideincludes an end that is proximate to and on the first side of the thirdsensing element; and the fourth magnetoresistive sensor comprising: afourth sensing element, and a fourth flux guide comprising a fourth softferromagnetic material, wherein the fourth soft ferromagnetic materialis a fourth high permeability magnetic material, wherein (i) the fourthflux guide is above or below the fourth sensing element of the fourthmagnetoresistive sensor in the first direction, (ii) the fourth fluxguide is disposed non-parallel to a first side of the fourth sensingelement, and (iii) the fourth flux guide includes an end that isproximate to and on the first side of the fourth sensing element,wherein the sensor further includes a plurality of cladded lines,wherein each cladded line is positioned adjacent to one of the first,second, third, and fourth flux guides, wherein each flux guide of thefirst, second, third, and fourth flux guides includes (i) a firstvertical segment, (ii) a second vertical segment, and (iii) a horizontalsegment connecting the first and second vertical segments, wherein afree end of the first vertical segment is flared away from a free end ofthe second vertical segment, each flux guide having the flared-away freeends at least partially enclosing the cladded line between the twovertical segments, and wherein the first vertical segment, the secondvertical segment, and the horizontal segment define an opening, theopening having a width defined by a distance between inner walls of thefirst and second vertical segments, wherein the width of the openingbetween the inner walls at the flare-away free ends is larger than thewidth of the opening between the inner walls at connected ends of thefirst and second vertical segments, the first and second verticalsegments being connected to the horizontal segment at the connectedends.
 23. The ferromagnetic thin-film based magnetic field sensor ofclaim 22, wherein each of the first, second, third, and fourth highpermeability magnetic materials is the same material.
 24. Theferromagnetic thin-film based magnetic field sensor of claim 22, whereinat least one of the first, second, third, and fourth high permeabilitymagnetic materials is nickel iron (NiFe).
 25. The ferromagneticthin-film based magnetic field sensor of claim 22, wherein each of thefirst, second, third, and fourth high permeability magnetic materials isnickel iron (NiFe).
 26. The ferromagnetic thin-film based magnetic fieldsensor of claim 22, wherein the first plurality of magnetoresistivesensors is connected to form a circuit, and wherein the circuit includesinput terminals configured to receive an electrical power and outputterminals connected to a voltage meter.
 27. The ferromagnetic thin-filmbased magnetic field sensor of claim 22, wherein the first plurality ofmagnetoresistive sensors is connected to form a circuit, and wherein thecircuit is configured to detect the magnetic field in the firstdirection.
 28. The ferromagnetic thin-film based magnetic field sensorof claim 22, wherein the first plurality of magnetoresistive sensors isconnected into a bridge circuit having input terminals and outputterminals.
 29. The ferromagnetic thin-film based magnetic field sensorof claim 28, wherein the input terminals are configured to receiveelectrical power and the output terminals are connected to a voltmeterto measure an output signal.
 30. The ferromagnetic thin-film basedmagnetic field sensor of claim 22, wherein the first and secondmagnetoresistive sensors are connected for differential measurement. 31.The ferromagnetic thin-film based magnetic field sensor of claim 22,wherein the first and second magnetoresistive sensors are connected to,in operation, subtract resistances of the first and secondmagnetoresistive sensors.
 32. The ferromagnetic thin-film based magneticfield sensor of claim 22, wherein the first and second magnetoresistivesensors are connected to, in operation, produce a response when sensinga magnetic field in a second direction orthogonal to the firstdirection.
 33. The ferromagnetic thin-film based magnetic field sensorof claim 22, wherein the first and second magnetoresistive sensors areconnected to, in operation, eliminate a magnetic field response in asecond direction orthogonal to the first direction.
 34. Theferromagnetic thin-film based magnetic field sensor of claim 22, whereinthe first and second magnetoresistive sensors are connected to, inoperation, double a magnetic field measurement in the first direction.35. The ferromagnetic thin-film based magnetic field sensor of claim 22,wherein each of the first, second, third, and fourth magnetoresistivesensors is a magnetic tunnel junction sensor.
 36. The ferromagneticthin-film based magnetic field sensor of claim 22, wherein theferromagnetic thin-film based magnetic field sensor is configured togenerate a sensor signal, and wherein the magnetic field in the firstdirection is determined based on the sensor signal.
 37. Theferromagnetic thin-film based magnetic field sensor of claim 22, furthercomprising: a second plurality of magnetoresistive sensors configured tobe electrically connected together to sense a magnetic field in a seconddirection orthogonal to the first direction.
 38. The ferromagneticthin-film based magnetic field sensor of claim 22, further comprising: asecond plurality of magnetoresistive sensors configured to beelectrically connected together to sense a magnetic field in a seconddirection orthogonal to the first direction; and a third plurality ofmagnetoresistive sensors configured to be electrically connectedtogether to sense a magnetic field in a third direction orthogonal tothe first and second directions.
 39. The ferromagnetic thin-film basedmagnetic field sensor of claim 22, wherein the first magnetoresistivesensor further includes a first reference layer, the secondmagnetoresistive sensor further includes a second reference layer, thethird magnetoresistive sensor further includes a third reference layer,and the fourth magnetoresistive sensor further includes a fourthreference layer.
 40. The ferromagnetic thin-film based magnetic fieldsensor of claim 22, wherein at least one of the first, second, third,and fourth flux guides is configured as a bar.
 41. The ferromagneticthin-film based magnetic field sensor of claim 22, wherein the first andthird flux guides are above the first and third sensing elements,respectively, and wherein the second and fourth flux guides are belowthe second and fourth sensing elements, respectively.
 42. Theferromagnetic thin-film based magnetic field sensor of claim 22, whereineach of the first, second, third, and fourth sensing elements includes asecond side opposite to the first side, and wherein the first and thirdflux guides are above the first sides of the first and third sensingelements, respectively, and wherein the second and fourth flux guidesare below the second sides of the second and fourth sensing elements,respectively.
 43. A ferromagnetic thin-film based magnetic field sensorcomprising: a first plurality of magnetoresistive sensors coupledtogether, wherein each magnetoresistive sensor of the first plurality ofmagnetoresistive sensors comprises in an order in a direction: areference layer, an intermediate layer, and a sensing element; and oneor more flux guides, wherein each flux guide of the one or more fluxguides includes a soft ferromagnetic material, wherein the softferromagnetic material is a high permeability magnetic material, whereinat least one flux guide of the one or more flux guides is associatedwith at least one magnetoresistive sensor of the first plurality ofmagnetoresistive sensors, and wherein (i) the at least one flux guide isin a plane that is above or below the at least one magnetoresistivesensor and parallel to the sensing element of the at least onemagnetoresistive sensor, (ii) the at least one flux guide is disposednon-parallel to a first side of the at least one magnetoresistivesensor, and (iii) the at least one flux guide includes an end that isproximate to a first edge and on the first side of the at least onemagnetoresistive sensor, wherein the sensor further includes a pluralityof cladded lines, wherein each cladded line is positioned adjacent to aflux guide of the one or more flux guides, wherein each flux guide ofthe one or more flux guides includes (i) a first vertical segment, (ii)a second vertical segment, and (iii) a horizontal segment connecting thefirst and second vertical segments, and wherein a free end of the firstvertical segment is flared away from a free end of the second verticalsegment, each flux guide having the flared-away free ends at leastpartially enclosing the cladded line between the two vertical segments,and wherein the first vertical segment, the second vertical segment, andthe horizontal segment define an opening, the opening having a widthdefined by a distance between inner walls of the first and secondvertical segments, wherein the width of the opening between the innerwalls at the flare-away free ends is larger than the width of theopening between the inner walls at connected ends of the first andsecond vertical segments, the first and second vertical segments beingconnected to the horizontal segment at the connected ends.
 44. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereineach magnetoresistive sensor of the first plurality of magnetoresistivesensors is a magnetic tunnel junction sensor.
 45. The ferromagneticthin-film based magnetic field sensor of claim 43, wherein theintermediate layer is an insulating dielectric layer.
 46. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe first plurality of magnetoresistive sensors comprises a firstmagnetoresistive sensor, a second magnetoresistive sensor, a thirdmagnetoresistive sensor, and a fourth magnetoresistive sensor, whereinthe one or more flux guides comprises a first flux guide, a second fluxguide, a third flux guide, and a fourth flux guide, and wherein thefirst flux guide is associated with the first magnetoresistive sensor,the second flux guide is associated with the second magnetoresistivesensor, the third flux guide is associated with the thirdmagnetoresistive sensor, and the fourth flux guide is associated withthe fourth magnetoresistive sensor.
 47. The ferromagnetic thin-filmbased magnetic field sensor of claim 43, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor, asecond magnetoresistive sensor, a third magnetoresistive sensor, and afourth magnetoresistive sensor, wherein the one or more flux guidescomprises a first flux guide, a second flux guide, a third flux guide,and a fourth flux guide, and wherein the first flux guide is above thefirst magnetoresistive sensor, the second flux guide is below the secondmagnetoresistive sensor, the third flux guide is above the thirdmagnetoresistive sensor, and the fourth flux guide is below the fourthmagnetoresistive sensor.
 48. The ferromagnetic thin-film based magneticfield sensor of claim 43, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor, asecond magnetoresistive sensor, a third magnetoresistive sensor, and afourth magnetoresistive sensor, each of the first, second, third, andfourth magnetoresistive sensors including a first side and a second sideopposite to the first side, wherein the one or more flux guidescomprises a first flux guide, a second flux guide, a third flux guide, afourth flux guide, a fifth flux guide, a sixth flux guide, a seventhflux guide, and an eighth flux guide, and wherein the first flux guideis below the first side of first magnetoresistive sensor, the secondflux guide is above the second side of the first magnetoresistivesensor, the third flux guide is above the first side of the secondmagnetoresistive sensor, the fourth flux guide is below the second sideof the second magnetoresistive sensor, the fifth flux guide is below thefirst side of the third magnetoresistive sensor, the sixth flux guide isabove the second side of the third magnetoresistive sensor, the seventhflux guide is above the first side of the fourth magnetoresistivesensor, and the eighth flux guide is below the second side of the fourthmagnetoresistive sensor.
 49. The ferromagnetic thin-film based magneticfield sensor of claim 43, wherein the high permeability magneticmaterial is nickel iron (NiFe).
 50. The ferromagnetic thin-film basedmagnetic field sensor of claim 43, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor and asecond magnetoresistive sensor, and wherein the first and secondmagnetoresistive sensors are connected for differential measurement. 51.The ferromagnetic thin-film based magnetic field sensor of claim 43,wherein the first plurality of magnetoresistive sensors comprises afirst magnetoresistive sensor and a second magnetoresistive sensor, andwherein the first and second magnetoresistive sensors are connected to,in operation, subtract resistances of the first and secondmagnetoresistive sensors.
 52. The ferromagnetic thin-film based magneticfield sensor of claim 43, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor and asecond magnetoresistive sensor, and wherein the first and secondmagnetoresistive sensors are connected to, in operation, produce aresponse when sensing a magnetic field in a second direction orthogonalto the direction.
 53. The ferromagnetic thin-film based magnetic fieldsensor of claim 43, wherein the first plurality of magnetoresistivesensors comprises a first magnetoresistive sensor and a secondmagnetoresistive sensor, and wherein the first and secondmagnetoresistive sensors are connected to, in operation, eliminate amagnetic field response in a second direction orthogonal to thedirection.
 54. The ferromagnetic thin-film based magnetic field sensorof claim 43, wherein the first plurality of magnetoresistive sensorscomprises a first magnetoresistive sensor and a second magnetoresistivesensor, and wherein the first and second magnetoresistive sensors areconnected to, in operation, double a magnetic field measurement in thedirection.
 55. The ferromagnetic thin-film based magnetic field sensorof claim 43, further comprising: a second plurality of magnetoresistivesensors configured to be electrically connected together, wherein thefirst plurality of magnetoresistive sensors is configured to sense afirst magnetic field in the direction, and wherein the second pluralityof magnetoresistive sensors is configured to sense a second magneticfield in a second direction orthogonal to the direction.
 56. Theferromagnetic thin-film based magnetic field sensor of claim 43, furthercomprising: a second plurality of magnetoresistive sensors configured tobe electrically connected together; and a third plurality ofmagnetoresistive sensors configured to be electrically connectedtogether, wherein the first plurality of magnetoresistive sensors isconfigured to sense a first magnetic field in the direction, the secondplurality of magnetoresistive sensors is configured to sense a secondmagnetic field in a second direction orthogonal to the direction, andthe third plurality of magnetoresistive sensors is configured to sense amagnetic field in a third direction orthogonal to the direction and thesecond direction.
 57. The ferromagnetic thin-film based magnetic fieldsensor of claim 43, wherein the first plurality of magnetoresistivesensors is connected to form a circuit, and wherein the circuit isconfigured to detect a magnetic field in the direction.
 58. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe first plurality of magnetoresistive sensors is connected to form acircuit, and wherein the circuit includes input terminals configured toreceive an electrical power and output terminals connected to a voltagemeter.
 59. The ferromagnetic thin-film based magnetic field sensor ofclaim 43, wherein the first plurality of magnetoresistive sensors isconnected into a bridge circuit having input terminals and outputterminals.
 60. The ferromagnetic thin-film based magnetic field sensorof claim 59, wherein the input terminals are configured to receiveelectrical power and the output terminals are connected to a voltmeterto measure an output signal.
 61. The ferromagnetic thin-film basedmagnetic field sensor of claim 43, wherein the order in the directionincludes: the sensing element of each magnetoresistive sensor of thefirst plurality of magnetoresistive sensors being formed on or above theassociated intermediate layer of each magnetoresistive sensor, and theintermediate layer of each magnetoresistive sensor of the firstplurality of magnetoresistive sensors being formed on or above theassociated reference layer of each magnetoresistive sensor.
 62. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe order in the direction includes: the reference layer of eachmagnetoresistive sensor of the first plurality of magnetoresistivesensors being formed on or above the associated intermediate layer ofeach magnetoresistive sensor, and the intermediate layer of eachmagnetoresistive sensor of the first plurality of magnetoresistivesensors being formed on or above the associated sensing element of eachmagnetoresistive sensor.
 63. The ferromagnetic thin-film based magneticfield sensor of claim 43, wherein the reference layer of eachmagnetoresistive sensor includes a plurality of layers having a combinedthickness in a range of 10 to 1000 Å.
 64. The ferromagnetic thin-filmbased magnetic field sensor of claim 43, wherein the reference layer ofeach magnetoresistive sensor includes a plurality of layers having acombined thickness in a range of 250 to 350 Å.
 65. The ferromagneticthin-film based magnetic field sensor of claim 43, wherein the sensingelement includes a thickness in a range of 10 to 5000 Å.
 66. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe sensing element includes a thickness in a range of 10 to 60 Å. 67.The ferromagnetic thin-film based magnetic field sensor of claim 43,wherein the ferromagnetic thin-film based magnetic field sensor isconfigured to generate a sensor signal, and wherein a magnetic field inthe direction is determined based on the sensor signal.
 68. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe reference layer of each magnetoresistive sensor includes: aferromagnetic layer; and an antiferromagnetic layer.
 69. Theferromagnetic thin-film based magnetic field sensor of claim 43, whereinthe reference layer of each magnetoresistive sensor includes: aferromagnetic layer having a thickness in a range of 20 to 80 Å; and anantiferromagnetic layer having a thickness of approximately 200 Å. 70.The ferromagnetic thin-film based magnetic field sensor of claim 43,wherein the reference layer of each magnetoresistive sensor includes: aferromagnetic layer; and an antiferromagnetic layer includingiridium-manganese (IrMn) alloy or platinum-manganese (PtMn) alloy. 71.The ferromagnetic thin-film based magnetic field sensor of claim 43,wherein the reference layer of each magnetoresistive sensor includes: aferromagnetic layer including a three-layer structure; and anantiferromagnetic layer.
 72. A ferromagnetic thin-film based magneticfield sensor comprising: a first plurality of magnetoresistive sensorscoupled to sense a first magnetic field in a direction orthogonal to aplane of the first plurality of magnetoresistive sensors, wherein eachmagnetoresistive sensor of the first plurality of magnetoresistivesensors includes a sensing element; one or more flux guides, whereineach flux guide of the one or more flux guides includes a softferromagnetic material, wherein the soft ferromagnetic material is ahigh permeability magnetic material, wherein at least one flux guide ofthe one or more flux guides is associated with the sensing element of atleast one magnetoresistive sensor of the first plurality ofmagnetoresistive sensors, and wherein (i) the at least one flux guide isin a plane that is above or below the associated sensing element in thedirection and parallel to the associated sensing element, (ii) the atleast one flux guide is disposed non-parallel to a first side of the atleast one magnetoresistive sensor, and (iii) the at least one flux guideincludes an end that is proximate to a first edge of the associatedsensing element and on a first side of the associated sensing element;and a second plurality of magnetoresistive sensors configured to beelectrically connected together to sense a second magnetic fieldorthogonal to the first magnetic field; wherein each flux guide of theone or more flux guides includes (i) a first vertical segment, (ii) asecond vertical segment, and (iii) a horizontal segment connecting thefirst and second vertical segments, and wherein a free end of the firstvertical segment is flared away from a free end of the second verticalsegment, each flux guide having the flared-away free ends at leastpartially enclosing a cladded line between the two vertical segments,and wherein the first vertical segment, the second vertical segment, andthe horizontal segment define an opening, the opening having a widthdefined by a distance between inner walls of the first and secondvertical segments, wherein the width of the opening between the innerwalls at the flare-away free ends is larger than the width of theopening between the inner walls at connected ends of the first andsecond vertical segments, the first and second vertical segments beingconnected to the horizontal segment at the connected ends.
 73. Theferromagnetic thin-film based magnetic field sensor of claim 72, whereinthe high permeability magnetic material is nickel iron (NiFe).
 74. Theferromagnetic thin-film based magnetic field sensor of claim 72, whereinthe first plurality of magnetoresistive sensors is connected to form acircuit, and wherein the circuit includes input terminals configured toreceive an electrical power and output terminals connected to a voltagemeter.
 75. The ferromagnetic thin-film based magnetic field sensor ofclaim 72, wherein first plurality of magnetoresistive sensors isconnected into a bridge circuit having input terminals and outputterminals.
 76. The ferromagnetic thin-film based magnetic field sensorof claim 75, wherein the input terminals are configured to receiveelectrical power and the output terminals are connected to a voltmeterto measure an output signal.
 77. The ferromagnetic thin-film basedmagnetic field sensor of claim 72, wherein the sensing element of eachmagnetoresistive sensor is disposed adjacent to a reference layer, andwherein an intermediate layer is disposed between the sensing elementand the reference layer.
 78. The ferromagnetic thin-film based magneticfield sensor of claim 72, wherein the sensing element of eachmagnetoresistive sensor is disposed adjacent to a reference layer, andwherein an insulating dielectric layer is disposed between the sensingelement and the reference layer.
 79. The ferromagnetic thin-film basedmagnetic field sensor of claim 72, wherein each magnetoresistive sensorof the first plurality of magnetoresistive sensors is a magnetic tunneljunction sensor.
 80. The ferromagnetic thin-film based magnetic fieldsensor of claim 72, further comprising: a third plurality ofmagnetoresistive sensors electrically connected together to sense athird magnetic field orthogonal to the first and second magnetic fields.81. The ferromagnetic thin-film based magnetic field sensor of claim 72,wherein the first plurality of magnetoresistive sensors is connectedtogether to generate a sensor signal, and wherein the first magneticfield in the direction is determined based on the sensor signal.
 82. Theferromagnetic thin-film based magnetic field sensor of claim 72, whereinthe first plurality of magnetoresistive sensors comprises a firstmagnetoresistive sensor, a second magnetoresistive sensor, a thirdmagnetoresistive sensor, and a fourth magnetoresistive sensor, whereinthe one or more flux guides comprises a first flux guide, a second fluxguide, a third flux guide, and a fourth flux guide, and wherein thefirst flux guide is associated with the first magnetoresistive sensor,the second flux guide is associated with the second magnetoresistivesensor, the third flux guide is associated with the thirdmagnetoresistive sensor, and the fourth flux guide is associated withthe fourth magnetoresistive sensor.
 83. The ferromagnetic thin-filmbased magnetic field sensor of claim 72, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor, asecond magnetoresistive sensor, a third magnetoresistive sensor, and afourth magnetoresistive sensor, wherein the one or more flux guidescomprises a first flux guide, a second flux guide, a third flux guide,and a fourth flux guide, and wherein the first flux guide is above thefirst magnetoresistive sensor, the second flux guide is below the secondmagnetoresistive sensor, the third flux guide is above the thirdmagnetoresistive sensor, and the fourth flux guide is below the fourthmagnetoresistive sensor.
 84. The ferromagnetic thin-film based magneticfield sensor of claim 72, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor, asecond magnetoresistive sensor, a third magnetoresistive sensor, and afourth magnetoresistive sensor, each of the first, second, third, andfourth magnetoresistive sensors including a first side and a second sideopposite to the first side, wherein the one or more flux guidescomprises a first flux guide, a second flux guide, a third flux guide, afourth flux guide, a fifth flux guide, a sixth flux guide, a seventhflux guide, and an eighth flux guide, and wherein the first flux guideis below the first side of first magnetoresistive sensor, the secondflux guide is above the second side of the first magnetoresistivesensor, the third flux guide is above the first side of the secondmagnetoresistive sensor, the fourth flux guide is below the second sideof the second magnetoresistive sensor, the fifth flux guide is below thefirst side of the third magnetoresistive sensor, the sixth flux guide isabove the second side of the third magnetoresistive sensor, the seventhflux guide is above the first side of the fourth magnetoresistivesensor, and the eighth flux guide is below the second side of the fourthmagnetoresistive sensor.
 85. The ferromagnetic thin-film based magneticfield sensor of claim 72, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor and asecond magnetoresistive sensor, and wherein the first and secondmagnetoresistive sensors are connected for differential measurement. 86.The ferromagnetic thin-film based magnetic field sensor of claim 72,wherein the first plurality of magnetoresistive sensors comprises afirst magnetoresistive sensor and a second magnetoresistive sensor, andwherein the first and second magnetoresistive sensors are connected to,in operation, subtract resistances of the first and secondmagnetoresistive sensors.
 87. The ferromagnetic thin-film based magneticfield sensor of claim 72, wherein the first plurality ofmagnetoresistive sensors comprises a first magnetoresistive sensor and asecond magnetoresistive sensor, and wherein the first and secondmagnetoresistive sensors are connected to, in operation, produce aresponse when sensing the second magnetic field.
 88. The ferromagneticthin-film based magnetic field sensor of claim 72, wherein the firstplurality of magnetoresistive sensors comprises a first magnetoresistivesensor and a second magnetoresistive sensor, and wherein the first andsecond magnetoresistive sensors are connected to, in operation,eliminate a response generated when sensing the second magnetic field.89. The ferromagnetic thin-film based magnetic field sensor of claim 72,wherein the first plurality of magnetoresistive sensors comprises afirst magnetoresistive sensor and a second magnetoresistive sensor, andwherein the first and second magnetoresistive sensors are connected to,in operation, double a magnetic field measurement when sensing the firstmagnetic field.
 90. The ferromagnetic thin-film based magnetic fieldsensor of claim 72, wherein each magnetoresistive sensor furtherincludes a reference layer and an intermediate layer disposed betweenthe sensing element and the reference layer.
 91. The ferromagneticthin-film based magnetic field sensor of claim 72, wherein eachmagnetoresistive sensor further includes a reference layer, and whereinthe reference layer includes a plurality of layers having a combinedthickness in a range of 10 to 1000 Å.
 92. The ferromagnetic thin-filmbased magnetic field sensor of claim 72, wherein each magnetoresistivesensor further includes a reference layer, and wherein the referencelayer includes a plurality of layers having a combined thickness in arange of 250 to 350 Å.
 93. The ferromagnetic thin-film based magneticfield sensor of claim 72, wherein each magnetoresistive sensor furtherincludes a reference layer, and wherein the reference layer comprises: aferromagnetic layer; and an antiferromagnetic layer.
 94. Theferromagnetic thin-film based magnetic field sensor of claim 72, whereineach magnetoresistive sensor further includes a reference layer, andwherein the reference layer comprises: a ferromagnetic layer having athickness in a range of 20 to 80 Å; and an antiferromagnetic layerhaving a thickness of approximately 200 Å.
 95. The ferromagneticthin-film based magnetic field sensor of claim 72, wherein eachmagnetoresistive sensor further includes a reference layer, and whereinthe reference layer comprises: a ferromagnetic layer; and anantiferromagnetic layer including iridium-manganese (IrMn) alloy orplatinum-manganese (PtMn) alloy.
 96. The ferromagnetic thin-film basedmagnetic field sensor of claim 72, wherein each magnetoresistive sensorfurther includes a reference layer, and wherein the reference layercomprises: a ferromagnetic layer including a three-layer structure; andan antiferromagnetic layer.
 97. The ferromagnetic thin-film basedmagnetic field sensor of claim 72, wherein the sensing element includesa thickness in a range of 10 to 5000 Å.
 98. The ferromagnetic thin-filmbased magnetic field sensor of claim 72, wherein the sensing elementincludes a thickness in a range of 10 to 60 Å.
 99. The ferromagneticthin-film based magnetic field sensor of claim 72, wherein theferromagnetic thin-film based magnetic field sensor is configured togenerate a sensor signal, and wherein the first magnetic field isdetermined based on the sensor signal.